A viable microorganism composition is needed for addition to mixed feed in order to increase growth and improve feed efficiency of livestock by maintaining a balance of intestinal microbial flora which plays an important role in nutritional actions such as the metabolism of nutrients and the synthesis of vitamins. Viable microorganism compositions can be effective only if they reach the digestive tract, and hence stability in storage feed and stability under acid and alkaline conditions and under heating are essential. Spore-forming viable microorganisms belonging to genus Bacillus are preferably used for that purpose.
Pellet-type feed has a number of advantages: for example, each pellet is a complete feed unit with homogenized feed components. The availability of nutrients in the feed is increased. The palatability of the feed is improved. Body weight gain and feed efficiency are improved. The feed is less bulky and so is easy to handle. Feeding time and labor can be saved, and the waste of feed by blowing off in the wind and spilling is minimized. As a result of these advantages pellet-type feed is quite popular. Since the pellets are manufactured by formulating previously pulverized feed components and pelleting with pressure and steam by means of a pellet-mill, even the relatively heat stable spore-forming microorganisms such as genus Bacillus are partially destroyed and lose viability due to the effects of steam heating, generated heat, pressure and water content; and hence there is the disadvantage that a large proportion of the viable microorganisms is lost.